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Re: Collection Synchronization for WebDAV

From: Werner Donné <werner.donne@re.be>
Date: Wed, 04 Jul 2007 10:27:04 +0200
Message-ID: <468B59D8.2050301@re.be>
To: Cyrus Daboo <cyrus@daboo.name>
Cc: w3c-dist-auth@w3.org

Hi Cyrus,

When I want to sync my client with my server I send a PROPFIND
with depth infinity for the property getlastmodified. This
requires only one round-trip. When I do this on a collection
which returns about 5000 resources the result is 870KB. That is
too large indeed. With compression on, however, it is below 20KB.
This is no longer a scalability problem.

The implementation of this specification introduces a lot of
bookkeeping at the server side. I doubt if it is worth the gain
in reality.

About the spec itself:

3. Open Issues

1. Yes. This can save a GET if the reason for the update was an
    update of only properties.

2. Yes, otherwise you would have to fetch all properties.

3. This seems dangerous. This is only useful to try to save a GET
    by mimicking the operation at the client side. This cannot be
    done accurately in all cases, because the client has no control
    over the way properties are copied, for example.

4. Only if you support the MOVE in item 3.

5. Losing the "read" privilege on a resource doesn't imply its
    presence can no longer be seen in the collection it is in.
    In some implementations it does, but then it is still not
    correct to return a deletion, because the client could later
    try to recreate the resource. This would have to fail because
    the invisible resource still exists.

6. In a versioning system deletion followed by recreation can't be
    considered as the change of an existing resource. The deleted
    one may be removed from the collection, but it might still exist.

5.1.3. DAV:sync-response XML Element

Why is this element introduced? You can make sync-token optional and
stick with "response". That expresses as much as the modified multistatus
content model.



Cyrus Daboo wrote:
> Hi folks,
> FYI. Comments welcome.
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
>     Title        : Collection Synchronization for WebDAV
>     Author(s)    : C. Daboo
>     Filename    : draft-daboo-webdav-sync-00.txt
>     Pages        : 14
>     Date        : 2007-7-3
>   This specification defines an extension to WebDAV that allows
>   efficient synchronization of the contents of a WebDAV collection.
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-daboo-webdav-sync-00.txt

Werner Donné  --  Re
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tel: (+32) 486 425803	e-mail: werner.donne@re.be
Received on Wednesday, 4 July 2007 08:30:41 UTC

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